content: /**
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
   * compliance with the License. You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software distributed under the License is
   * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
   * the License for the specific language governing permissions and limitations under the License.
   */
  
  package io.reactivex.flowable.internal.subscribers;
  
  import java.util.concurrent.atomic.*;
  
  import org.reactivestreams.Subscriber;
  
  import hu.akarnokd.reactivestreams.extensions.RelaxedSubscriber;
  import io.reactivex.common.Disposable;
  import io.reactivex.common.exceptions.MissingBackpressureException;
  import io.reactivex.flowable.internal.queues.SimplePlainQueue;
  import io.reactivex.flowable.internal.subscriptions.SubscriptionHelper;
  import io.reactivex.flowable.internal.utils.*;
  
  /**
   * Abstract base class for subscribers that hold another subscriber, a queue
   * and requires queue-drain behavior.
   *
   * @param <T> the source type to which this subscriber will be subscribed
   * @param <U> the value type in the queue
   * @param <V> the value type the child subscriber accepts
   */
  public abstract class QueueDrainSubscriber<T, U, V> extends QueueDrainSubscriberPad4 implements RelaxedSubscriber<T>, QueueDrain<U, V> {
      protected final Subscriber<? super V> actual;
      protected final SimplePlainQueue<U> queue;
  
      protected volatile boolean cancelled;
  
      protected volatile boolean done;
      protected Throwable error;
  
      public QueueDrainSubscriber(Subscriber<? super V> actual, SimplePlainQueue<U> queue) {
          this.actual = actual;
          this.queue = queue;
      }
  
      @Override
      public final boolean cancelled() {
          return cancelled;
      }
  
      @Override
      public final boolean done() {
          return done;
      }
  
      @Override
      public final boolean enter() {
          return wip.getAndIncrement() == 0;
      }
  
      public final boolean fastEnter() {
          return wip.get() == 0 && wip.compareAndSet(0, 1);
      }
  
      protected final void fastPathEmitMax(U value, boolean delayError, Disposable dispose) {
          final Subscriber<? super V> s = actual;
          final SimplePlainQueue<U> q = queue;
  
          if (wip.get() == 0 && wip.compareAndSet(0, 1)) {
              long r = requested.get();
              if (r != 0L) {
                  if (accept(s, value)) {
                      if (r != Long.MAX_VALUE) {
                          produced(1);
                      }
                  }
                  if (leave(-1) == 0) {
                      return;
                  }
              } else {
                  dispose.dispose();
                  s.onError(new MissingBackpressureException("Could not emit buffer due to lack of requests"));
                  return;
              }
          } else {
              q.offer(value);
              if (!enter()) {
                  return;
              }
          }
          QueueDrainHelper.drainMaxLoop(q, s, delayError, dispose, this);
      }
  
      protected final void fastPathOrderedEmitMax(U value, boolean delayError, Disposable dispose) {
          final Subscriber<? super V> s = actual;
          final SimplePlainQueue<U> q = queue;
  
          if (wip.get() == 0 && wip.compareAndSet(0, 1)) {
              long r = requested.get();
              if (r != 0L) {
                  if (q.isEmpty()) {
                      if (accept(s, value)) {
                          if (r != Long.MAX_VALUE) {
                              produced(1);
                          }
                      }
                      if (leave(-1) == 0) {
                          return;
                      }
                  } else {
                      q.offer(value);
                  }
              } else {
                  cancelled = true;
                  dispose.dispose();
                  s.onError(new MissingBackpressureException("Could not emit buffer due to lack of requests"));
                  return;
              }
          } else {
              q.offer(value);
              if (!enter()) {
                  return;
              }
          }
          QueueDrainHelper.drainMaxLoop(q, s, delayError, dispose, this);
      }
  
      @Override
      public boolean accept(Subscriber<? super V> a, U v) {
          return false;
      }
  
      @Override
      public final Throwable error() {
          return error;
      }
  
      @Override
      public final int leave(int m) {
          return wip.addAndGet(m);
      }
  
      @Override
      public final long requested() {
          return requested.get();
      }
  
      @Override
      public final long produced(long n) {
          return requested.addAndGet(-n);
      }
  
      public final void requested(long n) {
          if (SubscriptionHelper.validate(n)) {
              BackpressureHelper.add(requested, n);
          }
      }
  
  }
  
  // -------------------------------------------------------------------
  // Padding superclasses
  //-------------------------------------------------------------------
  
  /** Pads the header away from other fields. */
  class QueueDrainSubscriberPad0 {
      volatile long p1, p2, p3, p4, p5, p6, p7;
      volatile long p8, p9, p10, p11, p12, p13, p14, p15;
  }
  
  /** The WIP counter. */
  class QueueDrainSubscriberWip extends QueueDrainSubscriberPad0 {
      final AtomicInteger wip = new AtomicInteger();
  }
  
  /** Pads away the wip from the other fields. */
  class QueueDrainSubscriberPad2 extends QueueDrainSubscriberWip {
      volatile long p1a, p2a, p3a, p4a, p5a, p6a, p7a;
      volatile long p8a, p9a, p10a, p11a, p12a, p13a, p14a, p15a;
  }
  
  /** Contains the requested field. */
  class QueueDrainSubscriberPad3 extends QueueDrainSubscriberPad2 {
      final AtomicLong requested = new AtomicLong();
  }
  
  /** Pads away the requested from the other fields. */
  class QueueDrainSubscriberPad4 extends QueueDrainSubscriberPad3 {
      volatile long q1, q2, q3, q4, q5, q6, q7;
      volatile long q8, q9, q10, q11, q12, q13, q14, q15;
  }
  